US 4,575,611 AGranted

Method of joining pipes

AssigneeGeneral Electric Company

InventorDonald C. Bertossa

Life of this patent

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Abstract

A method of replacing a defective circumferential butt joint in a metal pipe is disclosed. An annular metal bridge ring, having a smaller wall thickness than the pipe but the same inside diameter, is positioned coaxial with the pipe in the relatively wide gap created by the removal of the defective joint. The ring becomes an integral part of the weld by being welded in place, thereby partially filling the gap between the edge surfaces of the pipe exposed by the removal of the defective joint. Subsequent layers of fusible material are weld deposited in place on top of the ring until the gap is filled to the exterior pipe surface. Use of the ring in the gap enables replacement of the defective joint with a single weld.

Claims29

Dependent claims

A method of joining a pair of metal pipe sections having substantially equal inside and outside diameters, said pipe sections being positioned such that a pair of pipe edge surfaces coaxially confront each other and define a circumferential gap therebetween, said method comprising the steps of:

positioning an annular metal bridge ring in said gap coaxially with said pipe sections, said ring having a smaller wall thickness than said pipe sections, the interior surfaces of said ring and said pipe sections having substantially the same diameter, said ring further including a pair of ring edge surfaces each facing one of said pipe edge surfaces;
providing an atmosphere of inert gas inside said pipe sections and said ring to inhibit oxidation in the area of said gap during subsequent fusing steps;
positioning fusible inserts on opposite sides of said ring, each of said inserts being bracketed by a pair of edge surfaces belonging to said ring and one of said pipe sections;
fusing each of said inserts to its bracketing pair of edge surfaces wherein portions of the inserts and bracketing edge surfaces make contact to provide a root layer therebetween and to thereby contact portions of said pair of coaxially confronting pipe edge surfaces through the metal bridge ring;
depositing at least one additional layer of fusible material by welding on each of said root layers between said bracketing edge surfaces up to a predetermined thickness, each of said additional layers coaxially encircling its underlying surface and being fused by welding thereto and to the contacted portions of said bracketing edge surfaces;
removing said inert gas atmosphere;
and
depositing further layers of a fusible material by welding in said gap and fusing said material to the underlying surfaces and to the contacted portions of said pipe edge surfaces, each of said further wedling layers extending throughout the full width of said gap and coaxially encircling its underlying surface. said further layers being successively deposited until said gap is filled substantially to the level of the exterior surfaces of said pipe sections and a unitary pipe is formed.

5 more elements

A method of replacing a defective butt weld in a metal pipe, said butt weld being bracketed by a pair of adjacent weld heat-affected zones, said method comprising the step of:

removing said butt weld and said heat-affected zones from said pipe to provide a circumferential gap between a pair of coaxial, confronting pipe edge surfaces;
shaping each of said confronting pipe edge surfaces to a predetermined configuration;
positioning an annular metal bridge ring in said gap coaxial with said pipe, said ring having a smaller wall thickness than said pipe and an interior diameter substantially equal to the interior pipe diameter, said ring including a pair of edge surfaces each having a predetermined configuration and facing one of said pipe edge surfaces;
providing an atmosphere of inert gas inside said pipe to inhibit oxidation in the area of said gap during subsequent fusing steps;
positioning fusible inserts on opposite sides of said ring, each of said inserts being bracketed by a pair of edge surfaces belonging to said ring and said pipe respectively;
fusing each of said inserts to its bracketing pair of edge surfaces whereby portions of the inserts and bracketing edge surfaces make contact to provide a root layer therebetween and to thereby contact portions of said pair of coaxially confronting pipe edge surfaces through the metal bridge ring;
depositing additional layers of fusible material by welding on each of said root layers between said bracketing edge surfaces up to a predetermined thickness, each of said additional layers coaxially encircling its underlying surface and being fused by welding thereto and to the contacted portions of said bracketing edge surfaces;
removing said inert gas atmosphere;
and
depositing further layers of a fusible material by welding in said gap and fusing said material to the underlying surface and to the contacted portions of said pipe edge surfaces, each of said further welding layers extending throughout the full width of said gap and coaxially encircling its underlying surface, said further layers being successively deposited until said gap is filled substantially to the level of the exterior surface of said pipe and the integrity of said pipe is reestablished.

7 more elements

A method of replacing a defective butt weld in a metal pipe consisting substantially of austenitic stainless steel, said butt weld being bracketed by a pair of adjacent weld heat-affected zones, said method comprising the steps of:

removing said butt weld and said heat-affected zones from said pipe to provide a circumferential gap between a pair of pipe sections having coaxially confronting pipe edge surfaces;
machining said confronting pipe edge surfaces to provide a plurality of substantially planar, pipe edge surface portions within the wall thickness of each pipe section, respective pairs of said pipe edge surface portions being symmetrically disposed about the center of said gap, a pair of first pipe edge surface portions lying in a pair of mutually spaced planes substantially perpendicular to the common axis of said pipe sections to define a first gap section therebetween, a pair of second pipe edge surface portions extending outward in opposite axial directions from said first gap section, the remaining pipe edge surface portions each inclining outward such that the angle of inclination of said common axis is steepest for the pipe edge surface portions adjacent the exterior surface of said pipe;
inserting at least a pair of gas tight water soluble diaphragms through said gap into the interior of said pipe on opposite sides of said gap, each of said diaphragms having a diameter substantially equal to the inside diameter of said pipe;
adhering said diaphragms to the interior surface of said pipe on opposite sides of said gap to seal off the area of said gap;
positioning an annular bridge ring consisting substantially of austenitic stainless steel in said gap coaxial with said pipe, said ring having a smaller wall thickness than said pipe and an interior diameter substantially equal to the interior pipe diameter, said ring including a pair of edge surface each facing one of said pipe edge surface and being configured to provide a plurality of substantially planar ring edge surface portions within the wall thickness of said ring, respective pairs of said ring edge surface portions being symmetrically disposed about the center of said gap, a pair of multually spaced first ring edge surface portions substantially parallel to said first pipe edge surface portions and spaced from the latter to define a pair of narrow gap portions within said first gap section, a pair of second ring edge surface portions extending axially inward toward said gap center from said pair of gap portions, and a pair of third ring edge surface portions extending between said second ring edge surface portions and the exterior ring surface and inclining inward toward said gap center;
providing a small aperture between one of said bracketing pairs of edge surfaces;
piping an inert gas into said gap area through said aperture to inhibit oxidation inside said pipe in said gap area;
maintining said inert gas under positive pressure in said gap area inside said pipe;
positioning fusible inserts on opposite sides of said ring, each of said inserts being bracketed by a pair of edge surfaces belonging to said ring and said pipe sections, said inserts consisting substantially of a corrosion resistant, fusible material comparible with said stainless steel;
welding each of said inserts to its bracketing pair of edge surfaces whereby poritons of the inserts and bracketing edge surfaces make contact to provide a root layer of fusible material therebetween and to thereby contact portions of said pair of coaxially confronting pipe edge surfaces through the metal bridge ring;
depositing additional layers of said corrosion resistant, fusible material by welding on each of said root layers between said bracketing edge surface up to a predetermined thickness, said predetermined thickness being selected to prevent further fusion of said root layers during subsequent fusing operations, each of said additional layers being deposite by welding as a plurality of beads of said fusible material of substantially uniform thickness and being welded to its underlying layer and to the contacted portions of said bracketing edge surfaces, each of said additional layers coaxially encircling its underlying surface;
welding said aperture closed;
removing said inert gas atmopshere by washing said diaphragms and said gas away with water introduced into said said gap region;
providing a liquid coolant inside said pipe at least in said gap area, said coolant being adapted to act as a heat sink for locally applied heat;
and
depositing further layers of a fusible material in said gap by welding to the underlying surface and to the contacted portions of said pipe edge surfaces, said further layers consisting substantially of said corrosion resistant, fusible material compartible with said stainless steel, each of said further layer extending throughout the full width of said gap and coaxially encircling its underlying surface, said further layers each being deposited as a plurality of beads of substantially uniform thickness of said fusible material unitl said gap is filled substantially to the level of the exterior surface of said pipe and the integrity of said pipe is reestablished.

13 more elements

Dependencies are inferred from the claim text.

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Abstract

positioning an annular metal bridge ring in said gap coaxially with said pipe sections, said ring having a smaller wall thickness than said pipe sections, the interior surfaces of said ring and said pipe sections having substantially the same diameter, said ring further including a pair of ring edge surfaces each facing one of said pipe edge surfaces;
providing an atmosphere of inert gas inside said pipe sections and said ring to inhibit oxidation in the area of said gap during subsequent fusing steps;
positioning fusible inserts on opposite sides of said ring, each of said inserts being bracketed by a pair of edge surfaces belonging to said ring and one of said pipe sections;
fusing each of said inserts to its bracketing pair of edge surfaces wherein portions of the inserts and bracketing edge surfaces make contact to provide a root layer therebetween and to thereby contact portions of said pair of coaxially confronting pipe edge surfaces through the metal bridge ring;
depositing at least one additional layer of fusible material by welding on each of said root layers between said bracketing edge surfaces up to a predetermined thickness, each of said additional layers coaxially encircling its underlying surface and being fused by welding thereto and to the contacted portions of said bracketing edge surfaces;
removing said inert gas atmosphere;
and
depositing further layers of a fusible material by welding in said gap and fusing said material to the underlying surfaces and to the contacted portions of said pipe edge surfaces, each of said further wedling layers extending throughout the full width of said gap and coaxially encircling its underlying surface. said further layers being successively deposited until said gap is filled substantially to the level of the exterior surfaces of said pipe sections and a unitary pipe is formed.

5 more elements